On Fri, Sep 4, 2020, 12:48 Cade Brown firstname.lastname@example.org wrote:
I am positing that Python should contain a constant (similar to True, False, None), called Infinity.
It would be equivalent to `float('inf')`, i.e. a floating point value representing a non-fininte value. It would be the positive constant; negative infinity could retrieved via `-Infinity`
Or, to keep float representation the same, the name `inf` could be used, but that does not fit Python's normal choice for such identifiers (but indeed, this is what C uses which is the desired behavior of string conversion)
I think there are a number of good reasons for this constant. For example:
- It is also a fundamental constant (similar to True, False, and None),
and should be representable as such in the language
- Requiring a cast from float to string is messy, and also obviously
less efficient (but this performance difference is likely insignificant) * Further, having a function call for something that should be a constant is a code-smell; in general str -> float conversion may throw an error or anything else and I'd rather not worry about that.
- It would make the useful property that `eval(repr(x)) == x` for
floating point numbers (currently, `NameError: name 'inf' is not defined`)
This makes it difficult to, for example, naively serialize a list of floats. For example:
>>> x = [1, 2, 3, 4] >>> repr(x) '[1, 2, 3, 4]' >>> eval(repr(x)) == x True >>> x = [1, 2, 3, float('inf')] >>> repr(x) '[1, 2, 3, inf]' >>> eval(repr(x)) == x Traceback (most recent call last): File "<stdin>", line 1, in <module> File "<string>", line 1, in <module> NameError: name 'inf' is not defined
To me, this is problematic; I would expect it to work seamlessly as it does with other floating point constants.
A few rebuttals/claims against:
- Creating a new constant (Infinity) which is unassignable may break
It will break an ENORMOUS amount of code. Numpy has its own top-level "inf" variable. So all code that uses "from numpy import *" will break. Pylab imports numpy in that way, so "from pylab import *" will also break. Whether you think this is a good approach or not, a ton of tutorials recommend doing this. All of those tutorials will break in a way that is very hard to fix.